Rational use of fertilization and nutrient management in orchards

Abstract

國內水果生產肥料投入量極高，又未能有效地的執行土壤分析與植體營養診斷工作；在果農追求高產、高品質的企圖下，難免促成過度施肥的不當操作。調查資料顯示，國內若干果園存在土壤養分偏頗現象，表土酸化、土壤有效性磷偏高、土壤鉀素含量偏低等；同時果園葉片營養診斷資訊顯示，氮、磷濃度偏高而鉀、鎂濃度偏低。 評估果園營養狀態的工具，主要是土壤和植物體的調查與分析。多年生果樹的根系，相較於一年生的作物而言，分布在比較深的土壤剖面內，根在個別土層的分布與型態受該土層土壤肥力的影響而有不同，此外園區內土壤的變異也大，一般很難單獨依賴土壤的分析資料做為營養監測或是施肥推薦的工具。 利用葉片分析方法，診斷作物營養狀態，以其葉片取樣容易且變異較小，而成為較佳的方法。然而評估多年生木本果樹礦質要素的組態，原本就是一種挑戰，因為許多熱、亞熱帶果樹具有複雜以及易變的物候循環(phenological cycles)，影響果樹礦質要素的吸收與運移，加以果樹深廣的根系分布，使得例常性的表土分析無法提供足夠的資訊來評估土壤的供應量；另此樹體的組織與器官可以貯蓄礦質要素，緩衝許多短期的礦物質缺乏。雖然如此，累積長期多年的植體與土壤的分析資料，仍是建立營養管理對生產的影響關係的重要方法。 營養狀況之診斷固然不易，檢討改善營養管理以及設立合理化的施肥計畫更屬困難，唯有依據科學的原則與實際田間研究才能做好。施肥的最佳管理操作除了從經濟面考慮之外，同時必需考慮社會與環境。除了增加收益，同時需要維持或增進土壤品質、降低水環境之污染以及維護空氣品質。因而必須設立效能目標，研發施肥技術，以增進養分的效能兼顧產值與環境，建立合理化施肥管理體系。 為求增進肥料的效能、提高作物生產、增加收益、維持或增進土壤品質、降低污染、保護環境品質，建立果園營養診斷體系與營養管理方法亟待努力。本文謹就土壤肥力分析與植體營養診斷、施肥以及肥灌(fertigation)方法加以說明，期能對果樹栽培有所助益。 High fertilizer input and inefficient and limited use of soil test and plant analysis for nutrient diagnosis resulted in soil acidification and unbalanced soil nutrient status such as relatively high soil available phosphorous and low soil potassium content. Leaf nutrient diagnosis information also indicated very high content of nitrogen and phosphorous with relatively low content of potassium and magnesium prevailingly observed in Taiwan orchards. As fruit tree is perennial crop with root system distributed deeper within soil profile, thus be affected by soil fertility of different layers. Furthermore, the variation of soil fertility and property are large in orchard, fertilization recommendation and nutrient monitoring can not be solely dependant on soil testing. Hence plant analysis with leaf sampling of less variation seems to serve as a better tool for nutrient diagnosis. Yet, there are challenges and limitation for plant analysis, because complex and instable phenological cycles influencing uptake and translocation of inorganic nutrient, difficult assessment of soil supply capacity by routine soil test due to wide and deep root system and plant tissue or organs’ storage of nutrients buffering short term shortage of inorganic nutrient occurred in tropical and subtropical fruit trees. Nevertheless, yearly long-term accumulated analytical data still serve as an important tool to understand the relation between nutrient management and fruit production. Field study and research is in much need to be conducted to improve nutrient diagnosis .Establishment and promotion on rational use of fertilization and nutrient management have to deal with both commercial requirements and demands of social and natural environment. Not only upgrading the efficiency of fertilizer, raise the income and crop yields but efforts have to be made to maintain soil quality, reduce water and air pollution and conserve better quality of natural environment. Nutrient diagnosis of soil test and plant analysis together with fertilization methods including fertigation are to be discussed in detail looking forward to be beneficial to fruit cultivation